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Re: Operations on RDF datasets (ISSUE-111)

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Thu, 17 Jan 2013 11:14:48 +0000
Message-ID: <50F7DD28.5030204@epimorphics.com>
To: Ivan Herman <ivan@w3.org>
CC: public-rdf-wg@w3.org


On 17/01/13 10:51, Ivan Herman wrote:
>
> On Jan 16, 2013, at 21:00 , Andy Seaborne <andy.seaborne@epimorphics.com> wrote:
>
>>
>>
>> On 16/01/13 18:10, Richard Cyganiak wrote:
>>> As discussed in the call today, we need to decide whether to define any operations on RDF Datasets in the RDF Concepts document.
>>>
>>> There is a wiki page that lists some possible candidate operations, along with some discussion, pointers to possible definitions, etc.:
>>> http://www.w3.org/2011/rdf-wg/wiki/Dataset_Operations
>>>
>>> The candidate operations listed there are:
>>>
>>> * Isomorphism
>>
>> Include for testing otherwise no need.
>
> I am not sure I agree with 'no need': the RDF Semantics does define the equivalence of graphs, I think having a clear definition extended to dataset is, sort of, missing.
>
> Anyway, whatever the reason, I believe this one is a +1 for me.

equivalence/isomorphism is the one case where we might get agreement and 
it is needed testing.  Let's consider this one separately to the others.

>> The defn quoted in the telecon is fine but clearer if it says "there is a single isomorphism mapping for the dataset", not a separate mapping per graph.
>>
>> (which makes it an isomorphism from one set mixing quads and triples to another set)
>>
>>> * Union
>>> * Merge
>>> * Untrusting Merge
>>> * Equivalence
>>> * Entailment
>>> * Equality
>>> * Folding/Unfolding
>>> * Union Dataset and Merge Dataset
>>
>> No need.
>>
>> (reason - we don't have time nor want to reopen the dataset semantics discussions)
>>
>
> I am indeed a bit concerned about reopening discussions here. There
> is
also the argument that we should not add things to the standard for
which there is no stable community experience yet.
>
> However (without using telcon time) maybe it is worth considering
adding these into the note on Datasets that Antoine is writing. If there
is a group who is interested in finding a proper definition for those,
that is.
>
> Ivan

Are you suggesting all of the operations (sans iso/equiv) in that note?

The usage of labelling of URI for the named graph in each dataset may be 
different; it may be location snapshots at different times, etc etc. 
Groundhog Day.

(We might agree on definitions of syntactic operations and say "if the 
labelling style is the same but then we have to agree on whether it is 
the "right" operation to highlight.)

	Andy

>
>>>
>>> Any opinions? In particular, arguments *for* including some of this stuff? Candidate definitions, etc.?
>>>
>>> Best,
>>> Richard
>>>
>>
>
>
> ----
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> mobile: +31-641044153
> FOAF: http://www.ivan-herman.net/foaf.rdf
>
>
>
>
>
Received on Thursday, 17 January 2013 11:15:21 GMT

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